EP0838587B2 - Lightened piston - Google Patents

Description

The invention relates to a piston for a Internal combustion engine according to the preamble of the claim 1.

Such a piston is described in EP 0 385 390 A1 and typically has shank surfaces not all areas along the height of the Piston shaft completely cylindrical and in cross section are formed circular. Here is the piston shaft in an upper area largely cylindrical Designed to hold the space for in an internal combustion engine complete incipient combustion. To reduce the weight of the piston are the pin bosses for receiving the connecting rod in the direction the diameter of the piston shaft set back inside. This will change the areas of the pin bosses, which is indispensable for the reception of the piston pin are, of the shaft surface, so the outer Lateral surface of the piston inwards, to the piston axis added. Consequently, in the outer areas Material will be saved, and it will be a weight reduction reached.

Such a piston with inwardly offset However, pin bosses must also be at the level of the pin bosses and below the pin boss shaft sections have with which he after installation in the cylinder of an internal combustion engine at the Cylinder wall is applied. These shaft wall sections, the also referred to as load-bearing shaft wall sections as they are responsible for guiding the piston in the cylinder are thus in a lower area of the Piston shaft at radially opposite to the bolt axis Pages, namely on the print side on the one hand and on the counterpressure side, on the other hand. At these points provide these shaft wall sections for a support of the piston in the up- and Abbewegung in the cylinder, wherein the piston can tilt around the piston pin axis. In particular in this tilting movement in the top and bottom dead center Change with regard to the side with which the piston abuts against the cylinder wall, from the pressure to Counterpressure side or vice versa. This tilting movement is through the load-bearing shaft wall sections as far as necessary limited. In the generic piston has the Piston skirt in its lower area connecting walls on which are reset inside and in which the Bolts hubs are. These connecting walls extend to the lower edge of the piston skirt. Thus missing at the bottom the piston is a circumferential ring which is formed so that he the two opposite shaft wall sections connects with each other.

Such a piston ensured by the Material saving in the areas outside the recessed pin bosses have the ability to reduce the weight of the Considerably reduce the piston.

It is the object of the present invention, in a such piston further reduce the weight and at the same time the strength of the piston and meet the low noise requirements.

This task is accomplished by a piston with the characteristics of the Claim 1 solved.

Consequently, the two shaft wall sections are with a Dimension in the circumferential direction, so to speak a width formed, extending in the direction of the piston axis, that is about the height of the piston, changed. Furthermore, the Connecting walls designed so that they match the course of in Direction of the piston axis extending edges of Shaft wall sections follow. According to the invention, the width the two leg wall portions to the lower end of the piston skirt out larger is formed. The two connecting walls thus obliquely and inclined to each other, that their distance in a lower area larger is as in an upper area. In other words The connecting walls are somewhat conical to each other. By the invention over the height of the piston changing width dimension the shaft wall sections can be achieved that especially in those zones where the shaft wall sections can be formed narrower, further material can be saved. The possible Weight reduction is for the invention Pistons up to 15%.

According to the invention, the shaft wall sections designed so that they as a whole as a supporting Shaft wall sections are designed, and to the Shaft walls no zones are formed, the Support of the piston on the cylinder inner wall no Make contribution. Such areas are therefore for the strength is not required and will be in accordance with the Invention omitted. These are in particular around those areas that are more than 0.2mm are reset relative to the cylinder wall. As well the course of the shaft wall sections to the the elasticity of the piston made requirements be adjusted.

At the same time, this can mean that the bearing Shaft wall sections available if required are, ensure a good runnability for the piston become. In particular, this may for example can be achieved without shortening the piston skirt, the one possible measure to reduce weight represents, but carries the risk that the piston noises by tilting in the cold state considerably increase. Furthermore, by the inventive partial resetting in the area of the shaft wall sections a reduction in wall thickness or to avoid further reset of the pin bosses be what Although a weight saving effect, but the strength of the Piston significantly reduced. Consequently, with the invention the piston according to EP 0 385 390 A1 is improved to the effect that that in this piston over the entire height with a constant width trained shaft wall sections be narrowed in areas such that a noticeable Weight reduction without sacrificing strength and Support properties in the cylinder is achieved. As mentioned, the connecting walls are the course of the lateral Edges adapted to the skirt wall sections.

As mentioned, the two supporting shaft wall sections in terms of their dimension in the circumferential direction upwards formed rejuvenating. This means that the Shaft wall sections in a side view largely as inverted T are designed, and in a lower area are significantly wider than in an upper area, in which they are closed to the circumferentially adjacent trained area of the piston skirt. Further are the two in this preferred embodiment Connecting walls formed inclined upward to each other. Consequently, the distance between the two Connecting walls in a lower area greater than in an upper area, and by adjusting the orientation the two connecting walls to the lateral edges of Shaft wall sections is achieved that the strength of required for carrying shaft walls is guaranteed.

As mentioned, it is provided according to the invention, as possible to save a lot of material and thus weight, so that it is basically conceivable, of course, largely flowing transitions the supporting shaft wall sections in to spare all those areas for support on the cylinder inner wall are not required.

Although it is known from US 5 076 225, in a piston, in both the upper area and the lower area in Circumferentially has a circular cross-section and thus increased stability even in its lower part having, the leg wall sections with an over the height to provide the piston shaft variable width. One However, such piston can not with the generic Pistons are compared because of this piston by the its lower end trained encircling ring the Stability of the piston always in a lower range is guaranteed. Consequently, here can the Shaft wall sections readily with a variable Width is formed without the stability of the piston compromise. This measure is for the generic piston however, in terms of its strength and warranty the support in the cylinder inner wall substantially questionable and can according to the invention only thereby be balanced, that the connecting walls the course of in the direction of the piston axis extending edges of Shaft wall sections are formed following.

A similar piston is known from DE 41 22 921 A1. Here, the shaft wall sections are largely X-shaped designed, the lower area in turn by an am bottom edge of the piston circumferentially formed ring is formed. The shaft is thus left out in places and the connecting walls are in the area of the recesses also excluded. This, however, the strength of Shank wall sections affected to the effect that the Shaft surface is not always completely on the cylinder wall is applied. Rather, this is only by the inventive Training the connecting walls reached, which at no Job are omitted, but for a support of the carrying shaft wall sections the course of their lateral Follow edges.

Furthermore, in US 4,856,417 a piston is described by which a piston clatter is to be reduced. Here are the shaft wall sections tapering downwards overall formed, and also from this document no indication it can be seen that the skirt wall sections on the load-bearing shaft wall sections can be reduced and thus can be tapered upwards, what according to the invention to considerable weight savings leads.

Furthermore, US 5,448,942 describes a piston whose supporting areas of the shaft walls take the form of an inverted T have. The other, non-structural areas of However, shaft walls are also present on this piston, so that this piston is disadvantageous in terms of its weight is. This applies equally to the piston according to the US 5,058,489, in which also the shaft walls by the actual contact area with the cylinder wall and more Areas are formed so that the resulting piston is unnecessarily difficult.

Although in principle for the piston according to the invention suitable for a piston material is conceivable is preferably, the piston of light metal, for example Aluminum or an aluminum alloy, to train the Weight of the piston low by this choice of material hold.

It is intended that the lateral edges of the load-bearing Shaft wall sections in the course of their rejuvenation so curved form that the connecting walls with respect their course in the direction of the piston axis convexly curved are. Consequently, the two connecting walls are convex curved, and the lateral edges of the Shaft wall sections are in the side view to the outside curved.

Advantageous embodiments of the invention are in the further claims.

The shank wall sections are therefore preferably such formed so that they are in the area of their entire outer surface as a supporting shaft wall sections for the support of the Piston on a cylinder inner wall worry. This can, how described for the shaft wall sections each for each Place the one along the height of the piston stem Width dimensions are selected, which are responsible for the leadership of the Piston is absolutely necessary. On any other Areas of the skirt wall sections that are designed such that when installed in a cylinder by more than 0.2 mm can be reset relative to the cylinder wall can be waived. When installing in the cylinder with the mentioned distance to the cylinder inner wall afford these zones namely the shaft wall sections namely no contribution to carrying and supporting the piston on the cylinder wall.

For the piston according to the invention it is further preferred that the piston shaft in its upper, over the set back Bolts hubs protruding area, at its bottom is hollowed out. This measure is made possible by the fact that in the piston according to the invention, the pin hubs as far as possibly set back from the shaft walls. Consequently arises in this area a certain supernatant of the upper, cylindrical piston area. These areas in the zone of Piston pin axis are not for the support of the piston essentially because the piston is essentially only around the Piston pin axis can tilt, so that by a hollowing of the Overhang over the piston pin axis further material and Weight can be saved without the strength and the Endanger the support of the piston.

According to another preferred embodiment provided that the pin bosses for use with a Stufenpleuel stepped at their sides facing each other are formed. This measure is for the piston according to the invention particularly suitable when the supporting shaft walls tapered towards the top are formed. As a result, the two connecting walls inclined upward to each other, so that those too Zones in which the pin bosses are to be formed, especially in an upper area very far inwards are offset. Nevertheless, the necessary support surface for the To ensure piston pins are in this preferred Embodiment the pin bosses, as described, stepped formed so that the distance between the pin bosses in an upper area is lower than in a lower area Area. This is despite the extensive transfer of Bolts hubs inside the necessary support surface for the Piston pin guaranteed. When used with a Stufenpleuel or a Trapezplepleuel, which consequently in a upper area is formed narrower than in one lower area of its bolt hub, can through the piston according to the invention in this embodiment a particularly advantageous weight saving achieved while ensuring strength and function become.

Fig. 1

eine schematische perspektivische Ansicht des erfindungsgemäßen Kolbens in einer ersten Ausführungsform;

Fig. 2

eine Seitenansicht des in Fig. 1 dargestellten Kolbens;

Fig. 3

eine Schnittansicht des erfindungsgemäßen Kolbens in einer zweiten Ausführungsform; und

Fig. 4

eine Seitenansicht des erfindungsgemäßen Kolbens in einer dritten bevorzugten Ausführungsform.

The invention will be described in detail below with reference to exemplary embodiments illustrated in the drawings. Show it:

Fig. 1

a schematic perspective view of the piston according to the invention in a first embodiment;

Fig. 2

a side view of the piston shown in Figure 1;

Fig. 3

a sectional view of the piston according to the invention in a second embodiment; and

Fig. 4

a side view of the piston according to the invention in a third preferred embodiment.

The piston 10 shown in Fig. 1 has a Piston stem 16 and an upper, largely cylindrical trained area 14. In this upper one Area 14, i. the ring field area, the piston can 10 with one or more partially circumferential and parallel provided to the piston crown extending slots be. Below the cylindrical portion 14 are formed the pin bosses 24, the recording of the (not shown) piston pin during assembly serve the piston with a (not shown) connecting rod.

As can be clearly seen in Fig. 1, are in the generic piston, the two pin bosses 24th each in the direction of the diameter of the piston skirt 16 reset so that at the bottom of the upper portion 14 of the piston 10, an overhang 26th arises. By this reset the

Bolts hubs 24 may be in the area below of the overhang 26 on the generic piston Material can be saved, so that the weight of the piston 10 can be reduced.

In a lower portion of the piston are further two opposite shaft wall sections 16 formed, which form the piston skirt. In the drawing is only the one according to the chosen orientation the piston 10 located at the front shaft wall portion 16 to recognize. The two shaft wall sections 16 are interconnected by two connecting walls 18 connected, each between the lateral Edges 20, 22 of the skirt wall portions 16 formed are. In the selected for the Fig. 1 representation is again from the two connecting walls 18 only to recognize that connecting wall 18, the 1 left edge 20 of the front shaft wall portion 16 with the corresponding edge 20 of the rear shaft wall section connects. As in Fig. 1 can be seen, the two connecting walls extend 18 to the bottom of the piston shaft and are set back inside. In the two connecting walls 18 are also the bolt ends 24th

According to the invention, the two shaft wall sections 16 with a dimension in the circumferential direction, so to speak of a width, which changes in the direction of the piston axis. By this measure, it is possible according to the invention, in those areas of the skirt wall sections 16, for the support of the piston on a cylinder inner wall not required, additional material and to save weight. According to the invention both connecting walls 18 are further designed such that that they follow the course of the in the direction of the piston axis extending edges 20, 22 of the shaft wall portions 16 follow. According to the embodiment shown in FIG. 1, in which the two shaft wall sections 16 formed tapered upwards, results thus an arrangement of the connecting walls 18, at the latter arranged inclined to each other upwards are. In other words, there are the connecting walls 18 to a certain extent in an oblique position.

In the embodiment shown in Fig. 1 are the lateral edges 20, 22 of the bearing Shaft wall sections 16 also designed convexly curved. Consequently, the connecting walls 18 in Area of their surface, ie in the course of the lower Edge of the piston to below the overhang 26 convexly curved.

In the side view of Fig. 2 in one direction perpendicular to the piston pin axis 28 is the curved Course of the lateral edges 20, 22 of the front Shaft wall section 16 again clearly visible. Furthermore, it becomes clear from the side view of FIG. 2, as in the piston 10 according to the invention, the pin bosses 24 opposite the peripheral edge of the upper Section 14 are set back so that an overhang 26 is created. As mentioned, this retranslation offers the pin bosses 24 the possibility to the left and right in the area of the bolt axis 28 lying Zones to save material.

According to the invention achieved thereby Weight savings further increased by the the bolt axis 28 radially opposite sides trained shaft wall sections 16 not over their entire height have a width equal to the Support the piston 10 required widest Place corresponds. Rather, the shaft wall section 16 each formed only so wide along its height, as for the support of the piston 10 on a cylinder inner wall is required. For example, can according to the upwardly tapering shown in Fig. 2 Shaping the supporting shank wall sections 16 another significant weight reduction be achieved. From the view of Fig. 2 is further again clarified that on the inventive Piston 10 at its lower edge no in cross-section circular area is formed in his Dimensions corresponds to the upper region 14. Further are on the piston 10 along its circumference the formed recessed two connecting walls 18.

In Fig. 3 is an advantageous embodiment of shown in Figs. 1 and 2 piston 10 shown. On the one hand is taken in the area of the piston axis 30 Sectional view of Fig. 3 again the oblique course of the two connecting walls according to the invention 18 to recognize. This is from the convex curved course of the connecting walls 18 to recognize that the course of the edges (not shown) 20, 22 of the shaft wall portions 16 approximately in the Fig. 1 and 2 corresponds to the course shown. Furthermore, in the sectional view to recognize that the two pin bosses 24 each from the outer edge of the upper Area 14 are back, but over their entire height along the piston axis 30 the same Have width.

The piston 10 shown in Fig. 3 is further in the region of the overhang 26 of the upper region 14 provided with the recesses 32 via the pin bosses 24. These cavities can therefore be formed are because the upper portion 14, as described in this area has an overhang 26. Furthermore allows the inclination of the connecting walls 18, which increases the width of the overhang 26, the Forming the cavities 32. These cavities can either by milling out the cast piston or by pouring water already during casting be formed. By this measure can through the material savings in the area of the cavities 32 for the piston 10 according to the invention another Reduction of its weight can be achieved.

In Fig. 4 is another embodiment of the plunger 10 according to the invention. In this Embodiment, the piston 10 is suitable for use with a (not shown) Stufenpleuel. at a Stufenpleuel is the eyelet, in which the piston pin is recorded in an upper area narrower than in a lower area. Accordingly, the pin bosses 24 of FIG. 4 illustrated embodiment of the invention Designed piston 10. This means that the inner Edges 34 of the pin bosses 24 are designed such that they have a smaller distance in an upper area have, as in a lower area. By This measure can also be used in the event that the pin bosses are set back very far, for example in the embodiment shown in Fig. 4, up to the lateral edges 20, 22 of the shaft wall portion 16, for a sufficiently large storage area for the piston pin are taken care of. This is done by the Broadening of the pin bosses 24 in their upper areas reached. The same applies to so-called Trapezoidal connecting.

It should be noted that the connecting walls 18 not necessarily so straight between the formed to be connected shaft wall portions 16 must be that in the side and cross-sectional views Fig. 2 to 5 exclusively their outlines are recognizable. Rather, the connecting walls 18 in the area of the pin bosses 24 convex to the outside be formed so that in a bottom view after Curved outside "outline" of the connecting walls 18 would be apparent. Essential to the invention, however, is that the connecting walls 18 with respect to their in the Page and section views of recognizable outline the over the height of the piston 10 is changing Width of the shaft wall sections 16 follow. hereby can despite the recess of the shaft wall sections 18 in the zones not required for support a sufficient strength of the invention Piston 10 can be ensured.

Claims (4)

1. Piston (10), especially made of light metal, with:- a piston shaft (16),

   an upper essentially cylindrical area (14) forming the piston base,

   pin bosses (24), which are set back from the piston axis (30) in the direction of the pin axis (28),

   two shaft wall sections (16) thus constructed in a lower section of the essentially cylindrically constructed area (14) on radially opposite sides in relation to the pin axis (28), and

   two connecting walls (18) connecting the shaft wall sections (16), which are set back, in which the pin bosses (24) lie and which extend as far as the lower edge of the piston shaft,

   characterised in that

   the two shaft wall sections (16) are constructed as supporting shaft wall sections and that those areas that offer no assistance to the support of the piston (10) on the cylinder inner wall are left open,

   the two shaft wall sections (16) have lateral edges (20, 22), which are constructed to taper upwards in the direction of circumference in a largely corresponding manner with respect to their dimension, and

   the connecting walls (18) follow the thereby determined course of the edges (20, 22) of the shaft wall sections (16) running in the direction of the piston axis (30) in such a way that they incline upwards towards each other, and

   the lateral edges (20, 22) of the supporting shaft wall sections (16) are constructed to be curved in the course of their taper, and

   the connecting walls (18) are constructed to be curved convexly in the direction of the piston axis.
2. Piston according to claim 1, characterised in that the shaft wall sections (16) are constructed in such a way that in the area of their overall outer surface they ensure the support of the piston (10) on the cylinder wall as supporting shaft wall sections (16).
3. Piston according to claim 1 or 2, characterised in that the piston (10) is hollowed out on its underside (32) in the region (26) overlapping the set back pin bosses (24).
4. Piston according to at least one of the preceding claims, characterized in that the pin bosses (24) are constructed for use with a stepped connecting rod or trapezoidal connecting rod on its sides (34) turned towards each other, in such a way that the distance between the pin bosses (24) is smaller in an upper area than in a lower area.

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